If you are traveling to New Hampshire or New Jersey, one thing you will want to have is a bike.
Most areas are easier to access with a bike rather than a vehicle.
Hauling bikes with pop up campers is easy enough with a bike rack. You can have one that mounts to the rear of the popup or on top of a popup camper.
Many families tour the country with bikes attached to the camper for sightseeing after parking at the campgrounds.
A bike rack for 1987 popup camper might be a little different style than one for a 1988 RV or truck camper. There are many different types of bike haulers and you have different sizes to haul many bikes or a few bikes. If you have a family of bike riders with six bikes, you will probably need a deluxe model. For a few bikes, you mike just want a plain bike rack the fits the rear of the camper.
As I said, New Hampshire has a lot of traffic and getting to areas of interest might be easier with bikes as well as the biking trails they have at the campgrounds. You might even want to take the bikes along for the kids to have something to do beside swim and play all day. They can ride their bikes around the campgrounds and make new friends on the way.
Hauling bikes with pop up campers does not cause any problems you might think. If attached to the rear end, the air resistance is zero, while a top loader may catch the wind more, but not enough for you to notice. Wherever you go, taking the bikes along will always be a plus if you have kids especially. The weather always allows for bike riding wherever you travel.